1. Field of the Invention
The present invention relates generally to a fuel injection control system for an internal combustion engine, such as an automotive internal combustion engine. More specifically, the invention relates to a fuel injection control in transition for accelerating the engine. Further particularly, the invention relates precise measurement of engine load upon occurrence of engine acceleration demand.
2. Description of the Background Art
As is well known various types of fuel injection control systems have been developed and proposed in the recent years. The fuel injection controls becomes more and more precise in detection of fuel injection control parameters and higher and higher in responding to variation of the engine driving condition. One of the major task to be achieved by such fuel injection control systems is optimal engine performance in relation to the engine driving condition. Another important task for the fuel injection control systems is anti-pollution emission control.
In the modern fuel injection control systems, acceleration enrichment is performed in response to acceleration demand at high response and at a magnitude precisely corresponding to the magnitude of acceleration demand as measured In general, acceleration demand is detected by detecting a increasing rate of throttle valve open angle. An extra fuel injection amount is usually derived on the basis of extra amount of intake air measured by means of an air flow meter In engine accelerating state, the amount of intake air flow rate measured by the air flow meter tends to become greater than that actually introduced into the engine combustion chamber.
Namely, since the air flow meter is located at upstream of the throttle valve, intake air amount flowing into the collector is measured as extra amount of intake air. Furthermore, further extra amount of intake air due to presence of air induction inertia is measured by the air flow meter. As a result, overshooting occurs in measuring of the intake air flow amount Therefore, when the extra fuel injection amount is derived on the basis of the overshooting intake air flow amount, the fuel amount becomes excessive versus the intake air amount actually introduced into the engine combustion chamber. This establishes over-rich air/fuel mixture to significantly increase pollutant in the exhaust gas.